Vamos lá, nada de área de comentários sem graça em seu blog. Coloque seus comentários com estilo de balão.
Vá até o Modelo de seu blog, clique em Editar modelo
Não se esqueça de antes de começar salvar uma cópia de seu template, caso não dê certo, é só reinstalá-lo. Essa dica é para o template Simple, do novo Blogger, implementado em julho de 2011 
Agora procure por:
/* Comments
-----------------------------------------------
*/
.comments .comments-content .icon.blog-author {
background-repeat: no-repeat;
background-image: url(data:image/png;base64,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);
}
.comments .comments-content .loadmore a {
border-top: 1px solid $(widget.alternate.text.color);
border-bottom: 1px solid $(widget.alternate.text.color);
}
.comments .comment-thread.inline-thread {
background-color: $(post.footer.background.color);
}
.comments .continue {
border-top: 2px solid $(widget.alternate.text.color);
}
Substitua então pelo código abaixo:
/* Comments
----------------------------------------------- */
.comments{clear:both;margin-top:10px;margin-bottom:0;font-family:Arial;line-height:18px;font-size:13px}
.comments .comments-content{margin-bottom:16px;font-weight:normal;text-align:left}
.comments .comment .comment-actions a,.comments .comment .continue a{display:inline-block;margin:0 0 10px 10px;padding:0 15px;color:#424242 !important;text-align:center;text-decoration:none;background:#EF560B;border:1px solid #000;border-radius:2px;height:26px;line-height:28px;font-weight:normal;cursor:pointer}
.comments .comments-content .comment-thread ol{list-style-type:none;padding:0;text-align:none}
.comments .comments-content .inline-thread{padding:0}
.comments .comments-content .comment-thread{margin:8px 0}
.comments .comments-content .comment-thread:empty{display:none}
.comment-replies{margin-top:1em;margin-left:40px;background: #EF560B0}
.comments .comments-content .comment{margin-bottom:0;padding-bottom:0}
.comments .comments-content .comment:first-child{padding-top:16px}
.comments .comments-content .comment:last-child{border-bottom:0;padding-bottom:0}
.comments .comments-content .comment-body{position:relative}
.comments .comments-content .user{font-style:normal;font-weight:normal}
.comments .comments-content .user a{color:#0E6284;font-weight:normal;text-decoration:none}
.comments .comments-content .icon.blog-author{width:18px;height:18px;display:inline-block;margin:0 0 -4px 6px}
.comments .comments-content .datetime a{color:#000;font-size:12px;float:right;text-decoration:none}
.comment-content{margin:0 0 8px;padding:0 5px}
.comment-header{font-size:18px;background-color:#eee;border-bottom:1px solid #808080;padding:5px}
.comments .comments-content .owner-actions{position:absolute;right:0;top:0}
.comments .comments-replybox{border:none;height:230px;width:100%}
.comments .comment-replybox-thread{margin-top:0}
.comments .comment-replybox-single{margin-top:5px;margin-left:48px}
.comments .comments-content .loadmore a{display:block;padding:10px 16px;text-align:center}
.comments .thread-toggle{cursor:pointer;display:inline-block}
.comments .comments-content .loadmore{cursor:pointer;max-height:3em;margin-top:0}
.comments .comments-content .loadmore.loaded{max-height:0;opacity:0;overflow:hidden}
.comments .thread-chrome.thread-collapsed{display:none}
.comments .thread-toggle{display:inline-block}
.comments .thread-toggle .thread-arrow{display:inline-block;height:6px;width:7px;overflow:visible;margin:0.3em;padding-right:4px}
.comments .thread-expanded .thread-arrow{background:url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAc AAAAHCAYAAADEUlfTAAAAG0lEQVR42mNgwAfKy8v/48I4FeA0AacVDFQBAP9wJkE/KhUMAAAAAElFTkSuQmCC") no-repeat scroll 0 0 transparent}
.comments .thread-collapsed .thread-arrow{background:url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAA AcAAAAHCAYAAADEUlfTAAAAJUlEQVR42mNgAILy8vL/DLgASBKnApgkVgXIkhgKiNKJ005s4gDLbCZBiSxfygAAAAB JRU5ErkJggg==") no-repeat scroll 0 0 transparent}
.avatar-image-container{background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm8NYDijHjfUVsNBhSPrYGv9ZZdwiNvgF71wMwOAmNfKCA-Fasox5ZP9TFprV0gtPpJ9bilLX-6bg3ESY4VmqMKLy9jeE5YRihQ45Z19qz9SQ8qZsjdkIc5TfmAJJgTKUvnlh-a2ZrJBWu/s1600/EF560B.png) top right no-repeat;float:left;vertical-align:middle;overflow:hidden;width:65px !important;height:51px !important;max-width:65px !important;max-height:51px !important}
.comments .avatar-image-container img{padding:2px;border:1px solid #ccc;width:45px !important;height:45px !important;max-width:45px !important;max-height:45px !important}
.comments .comment-block{margin-left:65px;position:relative;border:5px solid #EF560B; background: #fff; border-radius:8px}
@media screen and (max-device-width:480px){.comments .comments-content .comment-replies{margin-left:0}}
Se quer o balão em outra cor, salve a imagem da seta em seu PC, depois hospede em seu blog.
Substitua então os códigos acima pelo código de sua preferência.
Vermelho= cor da borda
azul=endereço da imagem
laranja=.cor dos botões
#000000
#610BEF
#669466
#A9D1D7
#C00000
#C0C0C0
#EF560B
#FF40FF
#FFD543
